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Thread: COP heatpump air/water
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18-10-2021, 07:54 PM #1
COP heatpump air/water
Hi to everyone
My question is about COP
I now that the manufacturers calculate
Different out side temp for instance
+7, 0, -5, -10 and so on, +7 best and -10 worst COP
But if the outside temp is
+ 7, + 10, + 15
And we calculated
I suppose the COP is going to decrease
Please help me to come to conclusionLast edited by Seair; 18-10-2021 at 08:46 PM.
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18-10-2021, 09:15 PM #2
Re: COP heatpump air/water
COP or coefficient of performance is a measure of energy input v energy output.
It relates to how energy efficient the apparatus is at design conditions.
Obviously, as outdoor temperatures increase the efficiency increases.
Manufacturers COP figures are produced in controlled conditions and may not represent real life but allow you to make a choice when making a decision on which make to buy.
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18-10-2021, 10:31 PM #3
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18-10-2021, 10:42 PM #4
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18-10-2021, 11:24 PM #5
Re: COP heatpump air/water
COP not as good, but it is not “only” thing to focus on.
heating a lot better with higher SCT
could run less time to achieve required water temperature
water in could also be warmer, if ambient warmer
Heat pump in cold climate not always ideal
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19-10-2021, 06:17 AM #6
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19-10-2021, 07:45 AM #7
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19-10-2021, 03:22 PM #8
Re: COP heatpump air/water
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19-10-2021, 04:27 PM #9
Re: COP heatpump air/water
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There is a simplistic kW in to kW out ratio but that is generally used in sales and advertising.
The more technical would be calculations from a pH chart and that involves far too many parameters
to be able to give you the quick answer that you want.
The quick answer you want is "yes" if the ambient temperature rises then the COP will but only to a point
and not under all circumstances.
If you want water at say 45 degsC then your refrigerant in the condenser would be at least 7 or 8 degs higher
to get the heat flow, if the system was less efficient then that difference might be near 10 or 12 degs higher.
If you are condensing in the region of about 55 degsC average and you air ambient outside was 10 degsC
then you would need to evaporate at about 0 degsC.
The lift or difference between 0 degsC and 55 degsC is 55 but if you were in an outside temp of 14 degsC the the evaporator would be at about 4 degsC so the lift now or the difference now between +4 and +55 is 51.
There is less lift so the comp won't have to work as hard and therefore the power used will be slightly less.
The trouble is with air sourced is the ambient. The ambient very rarely stays exactly where you want it to so the COP is referred to as Energy Efficiency Ratio or EER and EER is calculated by dividing the input into the output. Because heat and electricity can both be measured in kW that means you can get a ratio of efficiency (EER) by dividing input power into output heat. The EER can now be used more realistically because EER then can allow for seasonal variations such as spring, summer, autumn and winter. Averaged over the year the EER becomes a SEER
Seasonal Energy Efficiency Ratio. and now you have a ratio of seasonal performance that can be compared like for like with other systems.
Not easy answer I'm affraid.
Rob
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